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1.
Vision Res ; 165: 143-151, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31751899

RESUMO

We investigated the effect of induced astigmatism on subjective best focus and on visual acuity in 28 subjects of different ages (pre-presbyopic and presbyopic) and with different refractive profiles (emmetropes and astigmats). Measurements were performed using a custom-developed Adaptive Optics system, which allowed correction of high order aberrations and induction of astigmatism (0.5, 1, 1.5 and 2.0 D; axis: 180°, 45° and 22.5°). Upon induction of astigmatism, best focus shifted towards negative values in pre-presbyopic emmetropic eyes (by -0.14 D for 0.5 D and by -0.33 D for 2.0 D), while it shifted towards positive values in presbyopes, both in emmetropic presbyopes (by +0.04 D for 0.50 D and by +0.16 D for 2.0 D) and in astigmatic presbyopes (by +0.23 D for 0.50 D and by +0.40 D for 2.0 D). Also, visual acuity was most sensitive to astigmatism induction in pre-presbyopic emmetropes and least sensitive in presbyopes, particularly when high order aberrations were corrected: visual acuity ratio with/without astigmatism was: 0.74/0.85/0.98 (for astigmatism induced at 180°) and 0.68/0.73/0.86 at 45°, for pre-presbyopic emmetropes/presbyopic emmetropes/presbyopic astigmats. These findings may be connected to long term exposure to astigmatism in astigmats and corrected presbyopes.

2.
PLoS One ; 14(8): e0221144, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31430328

RESUMO

Presbyopes can choose today among different corrections to provide them with functional vision at far and near, and the outcomes and patient satisfaction depend on the selection. In this study, we present a binocular and portable vision simulator, based on temporal multiplexing of two synchronized tunable lenses allowing see-through and programmable visual simulations of presbyopic corrections. Seventeen binocular corrections were tested: 3 Monofocal (Far, Intermediate, Near), 4 Simultaneous Vision (bifocal, trifocal), 2 Monovision (far and near in either eye) and 8 Modified Monovision corrections (Simultaneous vision in one eye, Monofocal in the other eye). Perceived visual quality was assessed through the simulated corrections in 8 cyclopleged subjects who viewed a composite realistic visual scene with high contrast letters and a landscape at far (4 m) and a high contrast text at intermediate (66 cm) and near (33 cm) distances. Perceptual scores were obtained on a scale of 0 to 5 (low to high perceived quality). Perceptual preference was assessed by judging 36 random image pairs (6 repetitions) viewed through 9 binocular presbyopic corrections using two-interval forced choice procedures. The average score, across far and near distances, was the highest for Monovision (4.4±0.3), followed by Modified Monovision (3.4±0.1), Simultaneous Vision (3.0±0.1) and Monofocal corrections (2.9±0.2). However, the mean difference between far and near was lower for Simultaneous Vision and Monovision (0.4±0.1 PS) than Modified Monovision (1.8±0.7) or monofocal corrections (3.3±1.5). A strong significant correlation was found between the perceptual scores and the percentages of energy in focus, for each correction and distance (R = 0.64, p<0.0001). Multivariate ANOVA revealed significant influence of observation distances (p<10-9) and patients (p = 0.01) on Perceptual Score. In conclusion, we have developed a binocular portable vision simulator that can simulate rapidly and non-invasively different combinations of presbyopic corrections. This tool has applications in systematic clinical evaluation of presbyopia corrections.

3.
Sensors (Basel) ; 19(5)2019 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-30818880

RESUMO

This manuscript describes the Microwave Interferometric Reflectometer (MIR) instrument, a multi-beam dual-band GNSS-Reflectometer with beam-steering capabilities built to assess the performance of a PAssive Reflectrometry and Interferometry System-In Orbit Demonstrator (PARIS-IoD) like instrument and to compare the performance of different GNSS-R techniques and signals. The instrument is capable of tracking up to 4 different GNSS satellites, two at L1/E1 band, and two at L5/E5 band. The calibration procedure of the up- and down-looking arrays is presented, the calibration performance is evaluated, and the results of the validation experiments carried out before the field experiments are shown in this paper.

4.
Sci Rep ; 9(1): 1539, 2019 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-30733540

RESUMO

Adaptive optics (AO) visual simulators based on deformable mirrors, spatial light modulators or optotunable lenses are increasingly used to simulate vision through different multifocal lens designs. However, the correspondence of this simulation with that obtained through real intraocular lenses (IOLs) tested on the same eyes has not been, to our knowledge, demonstrated. We compare through-focus (TF) optical and visual quality produced by real multifocal IOLs (M-IOLs) -bifocal refractive and trifocal diffractive- projected on the subiect's eye with those same designs simulated with a spatial light modulator (SLM) or an optotunable lens working in temporal multiplexing mode (SimVis technology). Measurements were performed on 7 cyclopleged subjects using a custom-made multichannel 3-active-optical-elements polychromatic AO Visual Simulator in monochromatic light. The same system was used to demonstrate performance of the real IOLs, SLM and SimVis technology simulations on bench using double-pass imaging on an artificial eye. Results show a general good correspondence between the TF performance with the real and simulated M-IOLs, both optically (on bench) and visually (measured visual acuity in patients). We demonstrate that visual simulations in an AO environment capture to a large extent the individual optical and visual performance obtained with real M-IOLs, both in absolute values and in the shape of through-focus curves.

5.
Physiol Plant ; 163(4): 530-551, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29607503

RESUMO

Somatic embryogenesis receptor-like kinase 1 (SERK1) is a membrane receptor that might serve as common co-regulator of plant cell differentiation processes by forming heterodimers with specific receptor-like kinases. The Coffea canephora SERK1 homolog (CcSERK1) was cloned in this work, and its early function in the transcription of embryogenesis master genes and of genes encoding proteins involved in auxin metabolism was investigated by externally manipulating its expression in embryogenic leaf explants, before the appearance of embryogenic structures. Overexpression of CcSERK1 early during embryogenesis caused an increase in the number of somatic embryos when the 55-day process was completed. Suppression of CcSERK1 expression by RNA interference almost abolished somatic embryogenesis. Real time-PCR experiments revealed that the transcription of the CcAGL15, CcWUS, CcBBM, CcPKL, CcYUC1, CcPIN1 and CcPIN4 homologs was modified in direct proportion to the expression of CcSERK1 and that only CcLEC1 was inversely affected by the expression levels of CcSERK1. The expression of the CcYUC4 homolog was induced to more than 80-fold under CcSERK1 overexpression conditions, but it was also induced when CcSERK1 expression was silenced. The level of CcTIR1 was not affected by CcSERK1 overexpression but was almost abolished during CcSERK1 silencing. These results suggest that CcSERK1 co-regulates the induction of somatic embryogenesis in Coffea canephora by early activation of YUC-dependent auxin biosynthesis, auxin transport mediated by PIN1 and PIN4, and probably auxin perception by the TIR1 receptor, leading to the induction of early-stage homeotic genes (CcAGL15, CcWUS, CcPKL and CcBBM) and repression of late-stage homeotic genes (CcLec1).


Assuntos
Coffea/genética , Coffea/metabolismo , Ácidos Indolacéticos/metabolismo , Proteínas Quinases/genética , Sementes/genética , Clonagem Molecular , Expressão Ectópica do Gene , Regulação da Expressão Gênica de Plantas , Família Multigênica , Filogenia , Folhas de Planta/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Proteínas Quinases/metabolismo , Sementes/crescimento & desenvolvimento , Transcrição Genética
6.
Neurocir.-Soc. Luso-Esp. Neurocir ; 28(4): 176-182, jul.-ago. 2017. graf, tab
Artigo em Espanhol | IBECS | ID: ibc-164411

RESUMO

Objetivo: Evaluar si las tasas de recurrencia y las supervivencias libres de recurrencia/progresión (RFS) son diferentes en meningiomas de grado I de la Organización Mundial de la Salud (OMS) sometidos a resecciones grado I, II, III y IV de la escala de Simpson. Materiales y métodos: Revisamos de manera retrospectiva los datos de los pacientes que se sometieron a tratamiento quirúrgico de meningiomas de grado I de la OMS localizados en la convexidad, hoz/parasagital y base de cráneo entre junio de 1991 y diciembre de 2011. En el caso de las resecciones grado IV de Simpson la cirugía se complementó con radiocirugía o radioterapia sobre el resto tumoral. Comparamos las tasas de recurrencia y las RFS de los diferentes grados de Simpson tanto de manera global como por localización. Resultados: En el estudio se incluyeron 208 meningiomas. No existieron diferencias significativas en las tasas de recurrencia y en las RFS entre los diferentes grados de Simpson. Por localización, tampoco detectamos diferencias entre los grados de resección. En meningiomas de convexidad, las tasas de recurrencia en los grados I y III fueron del 7 y del 33%, respectivamente (p=0,131). Conclusiones: Este estudio sugiere que las tasas de control tumoral son independientes de los grados de Simpson. En meningiomas de hoz/parasagital y de base de cráneo debe valorarse la agresividad quirúrgica frente a los riesgos de lesionar estructuras neurovasculares. En meningiomas de convexidad, el objetivo inicial debería ser una resección grado I


Object: The aim of this study is to assess if the recurrence rates and recurrence/progression-free survivals (RFS) are different after Simpson's grades I, II, III and IV resections in World Health Organization (WHO) grade I meningiomas. Material and methods: A retrospective review was conducted on the data of patients who underwent surgical treatment of WHO grade I meningiomas located in convexity, falx/parasagittal, and skull base (anterior/media/posterior) between June 1991 and December 2011. In Simpson's grade IV resections, surgical treatment was supplemented with radiotherapy/radiosurgery on the tumour remains. A comparison was made on the recurrence rates and RFSs between Simpson's grades I, II, III, and IV resections, both overall and in tumour subsets according to their location. Results: A total of 208 meningiomas were included in this study. There were no significant differences in recurrence rates and RFSs between Simpson's grades I, II, III, and IV. No significant differences were noted between the different degrees of Simpson in any of the location groups. In convexity meningiomas, the recurrence rates were 7% and 33% in Simpson's grades I and III resections, respectively (P=.131). Conclusions: It has been shown that the rates of tumour control in meningiomas are not related to Simpson grades. In falx/parasagittal and skull base meningiomas, more aggressive attempts of tumour resection must be balanced against the risks of damaging critical neurovascular structures. In convexity meningiomas, a Simpson's grade I resection should be attempted first


Assuntos
Humanos , Meningioma/cirurgia , Neoplasias Meníngeas/cirurgia , Recidiva Local de Neoplasia/epidemiologia , Estadiamento de Neoplasias , Resultado do Tratamento , Complicações Pós-Operatórias/epidemiologia , Intervalo Livre de Doença , Meningioma/classificação , Estudos Retrospectivos
7.
Neurocirugia (Astur) ; 28(4): 176-182, 2017.
Artigo em Espanhol | MEDLINE | ID: mdl-28242156

RESUMO

OBJECT: The aim of this study is to assess if the recurrence rates and recurrence/progression-free survivals (RFS) are different after Simpson's grades I, II, III and IV resections in World Health Organization (WHO) grade I meningiomas. MATERIAL AND METHODS: A retrospective review was conducted on the data of patients who underwent surgical treatment of WHO grade I meningiomas located in convexity, falx/parasagittal, and skull base (anterior/media/posterior) between June 1991 and December 2011. In Simpson's grade IV resections, surgical treatment was supplemented with radiotherapy/radiosurgery on the tumour remains. A comparison was made on the recurrence rates and RFSs between Simpson's grades I, II, III, and IV resections, both overall and in tumour subsets according to their location. RESULTS: A total of 208 meningiomas were included in this study. There were no significant differences in recurrence rates and RFSs between Simpson's grades I, II, III, and IV. No significant differences were noted between the different degrees of Simpson in any of the location groups. In convexity meningiomas, the recurrence rates were 7% and 33% in Simpson's grades I and III resections, respectively (P=.131). CONCLUSIONS: It has been shown that the rates of tumour control in meningiomas are not related to Simpson grades. In falx/parasagittal and skull base meningiomas, more aggressive attempts of tumour resection must be balanced against the risks of damaging critical neurovascular structures. In convexity meningiomas, a Simpson's grade I resection should be attempted first.


Assuntos
Neoplasias Meníngeas/cirurgia , Meningioma/cirurgia , Gradação de Tumores/métodos , Adulto , Idoso , Intervalo Livre de Doença , Feminino , Humanos , Masculino , Neoplasias Meníngeas/patologia , Meningioma/patologia , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/cirurgia , Estudos Retrospectivos
8.
Sensors (Basel) ; 17(1)2017 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-28106825

RESUMO

This work addresses the accuracy of the Global Navigation Satellite Systems (GNSS)-Reflectometry (GNSS-R) scatterometric measurements considering the presence of both coherent and incoherent scattered components, for both conventional GNSS-R (cGNSS-R) and interferometric GNSS-R (iGNSS-R) techniques. The coherent component is present for some type of surfaces, and it has been neglected until now because it vanishes for the sea surface scattering case. Taking into account the presence of both scattering components, the estimated Signal-to-Noise Ratio (SNR) for both techniques is computed based on the detectability criterion, as it is done in conventional GNSS applications. The non-coherent averaging operation is considered from a general point of view, taking into account that thermal noise contributions can be reduced by an extra factor of 0.88 dB when using partially overlapped or partially correlated samples. After the SNRs are derived, the received waveform's peak variability is computed, which determines the system's capability to measure geophysical parameters. This theoretical derivations are applied to the United Kingdom (UK) TechDemoSat-1 (UK TDS-1) and to the future GNSS REflectometry, Radio Occultation and Scatterometry on board the International Space Station (ISS) (GEROS-ISS) scenarios, in order to estimate the expected scatterometric performance of both missions.

9.
Brain Behav Immun ; 53: 1-15, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26216710

RESUMO

Tumor-infiltrating immune cells are part of a complex microenvironment that promotes and/or regulates tumor development and growth. Depending on the type of cells and their functional interactions, immune cells may play a key role in suppressing the tumor or in providing support for tumor growth, with relevant effects on patient behavior. In recent years, important advances have been achieved in the characterization of immune cell infiltrates in central nervous system (CNS) tumors, but their role in tumorigenesis and patient behavior still remain poorly understood. Overall, these studies have shown significant but variable levels of infiltration of CNS tumors by macrophage/microglial cells (TAM) and to a less extent also lymphocytes (particularly T-cells and NK cells, and less frequently also B-cells). Of note, TAM infiltrate gliomas at moderate numbers where they frequently show an immune suppressive phenotype and functional behavior; in contrast, infiltration by TAM may be very pronounced in meningiomas, particularly in cases that carry isolated monosomy 22, where the immune infiltrates also contain greater numbers of cytotoxic T and NK-cells associated with an enhanced anti-tumoral immune response. In line with this, the presence of regulatory T cells, is usually limited to a small fraction of all meningiomas, while frequently found in gliomas. Despite these differences between gliomas and meningiomas, both tumors show heterogeneous levels of infiltration by immune cells with variable functionality. In this review we summarize current knowledge about tumor-infiltrating immune cells in the two most common types of CNS tumors-gliomas and meningiomas-, as well as the role that such immune cells may play in the tumor microenvironment in controlling and/or promoting tumor development, growth and control.


Assuntos
Neoplasias Encefálicas/imunologia , Glioma/imunologia , Neoplasias Meníngeas/imunologia , Meningioma/imunologia , Animais , Linfócitos B/imunologia , Linfócitos B/patologia , Neoplasias Encefálicas/patologia , Citometria de Fluxo , Glioma/metabolismo , Glioma/patologia , Humanos , Linfócitos/imunologia , Linfócitos/patologia , Macrófagos/imunologia , Macrófagos/patologia , Neoplasias Meníngeas/metabolismo , Meningioma/metabolismo , Meningioma/patologia , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/patologia
11.
Oncotarget ; 6(13): 10671-88, 2015 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-25965831

RESUMO

Meningiomas are usually considered to be benign central nervous system tumors; however, they show heterogenous clinical, histolopathological and cytogenetic features associated with a variable outcome. In recent years important advances have been achieved in the identification of the genetic/molecular alterations of meningiomas and the signaling pathways involved. Thus, monosomy 22, which is often associated with mutations of the NF2 gene, has emerged as the most frequent alteration of meningiomas; in addition, several other genes (e.g., AKT1, KLF4, TRAF7, SMO) and chromosomes have been found to be recurrently altered often in association with more complex karyotypes and involvement of multiple signaling pathways. Here we review the current knowledge about the most relevant genes involved and the signaling pathways targeted by such alterations. In addition, we summarize those proposals that have been made so far for classification and prognostic stratification of meningiomas based on their genetic/genomic features.


Assuntos
Predisposição Genética para Doença/genética , Neoplasias Meníngeas/genética , Meningioma/genética , Neurofibromina 2/genética , Transdução de Sinais/genética , Cromossomos Humanos Par 22/genética , Humanos , Neoplasias Meníngeas/patologia , Meningioma/patologia , Modelos Genéticos , Monossomia
12.
Biomed Opt Express ; 6(3): 948-62, 2015 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-25798317

RESUMO

Longitudinal Chromatic Aberration (LCA) influences the optical quality of the eye. However, the reported LCA varies across studies, likely associated to differences in the measurement techniques. We present LCA measured in subjects using wavefront sensing, double-pass retinal images, and psychophysical methods with a custom-developed polychromatic Adaptive Optics system in a wide spectral range (450-950 nm), with control of subjects' natural aberrations. LCA measured psychophysically was significantly higher than that from reflectometric techniques (1.51 D vs 1.00 D in the 488-700 nm range). Ours results indicate that the presence of natural aberrations is not the cause for the discrepancies across techniques.

13.
Enferm Infecc Microbiol Clin ; 33(7): 496-8, 2015.
Artigo em Espanhol | MEDLINE | ID: mdl-25639904
14.
PLoS One ; 9(8): e104904, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25121496

RESUMO

Biomechanical properties are an excellent health marker of biological tissues, however they are challenging to be measured in-vivo. Non-invasive approaches to assess tissue biomechanics have been suggested, but there is a clear need for more accurate techniques for diagnosis, surgical guidance and treatment evaluation. Recently air-puff systems have been developed to study the dynamic tissue response, nevertheless the experimental geometrical observations lack from an analysis that addresses specifically the inherent dynamic properties. In this study a viscoelastic finite element model was built that predicts the experimental corneal deformation response to an air-puff for different conditions. A sensitivity analysis reveals significant contributions to corneal deformation of intraocular pressure and corneal thickness, besides corneal biomechanical properties. The results show the capability of dynamic imaging to reveal inherent biomechanical properties in vivo. Estimates of corneal biomechanical parameters will contribute to the basic understanding of corneal structure, shape and integrity and increase the predictability of corneal surgery.


Assuntos
Córnea/fisiologia , Ar , Fenômenos Biomecânicos , Elasticidade , Análise de Elementos Finitos , Humanos , Modelos Teóricos , Viscosidade
15.
FEBS Lett ; 588(18): 3501-10, 2014 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-25131930

RESUMO

Despite their differential cell tropisms, HIV-1 and HCV dramatically influence disease progression in coinfected patients. Macrophages are important target cells of HIV-1. We hypothesized that secreted HCV core protein might modulate HIV-1 replication. We demonstrate that HCV core significantly enhances HIV-1 replication in human macrophages by upregulating TNF-α and IL-6 via TLR2-, JNK-, and MEK1/2-dependent pathways. Furthermore, we show that TNF-α and IL-6 secreted from HCV core-treated macrophages reactivates monocytic U1 cells latently infected with HIV-1. Our studies reveal a previously unrecognized role of HCV core by enhancing HIV-1 infection in macrophages.


Assuntos
HIV-1/fisiologia , Interleucina-6/genética , Macrófagos/virologia , Fator de Necrose Tumoral alfa/genética , Proteínas do Core Viral/fisiologia , Replicação Viral , Coinfecção/virologia , Células HEK293 , Infecções por HIV/virologia , Hepatite C/virologia , Humanos , Interleucina-6/metabolismo , MAP Quinase Quinase Quinases/metabolismo , Sistema de Sinalização das MAP Quinases , Receptor 2 Toll-Like/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Regulação para Cima
16.
Rev. crim ; 55(2): 119-133, ago. 2013.
Artigo em Espanhol | LILACS | ID: lil-708169

RESUMO

A pesar de la heterogeneidad casuística existente a nivel internacional con relación al papel desempeñado por las Fuerzas Armadas, su dedicación y empleo (o la decisión de no hacerlo) en la lucha contra la delincuencia organizada en concreto genera, al día de hoy, no pocas controversias. Defensores y detractores esgrimen razones y argumentos para defender el rol que se desea otorgar a las Fuerzas Armadas (o arrogarse estas mismas, según cada caso), como proveedoras de seguridad ciudadana frente al crimen organizado. Su inicial empleo en la confrontación contra el tráfico de drogas por todo el mundo ha propiciado el debate sobre su plena inmersión en la lucha contra toda tipología de delincuencia organizada, lo cual ha generado, de facto, diversos escenarios. Se pretende hacer una reflexión al aire de los pros y contras que se derivan de la implicación de las Fuerzas Armadas en la lucha contra la criminalidad organizada, extraídos del análisis casuístico de los principales escenarios vigentes en el mundo, tratando de identificar cuál de todos los posibles marcos de actuación marcará la tendencia en la escena internacional, acerca de cuál debe ser el compromiso de las Fuerzas Armadas frente a la criminalidad organizada, y cómo deben ejecutarlo.


Despite the casuistic heterogeneity existing at the international level with respect to the role played by the Armed Forces around the world, their dedication and use (or the decision not to use them) in the fight specifically against organized crime triggers today many controversies. Both supporters and opponents put forward reasons and arguments to defend or attack the purpose of giving or denying the Armed Forces any such role. Their original use in the confrontation against drug trafficking worldwide has fostered the debate about their full immersion in the war against any and all typology of organized crime; this, in fact, has created diverse scenarios. The article is intended to throw a thought into the air about the pros and cons deriving from Armed Forces involvement in the fight against organized criminality as taken from the casuistic analysis of the main scenarios still in force in the world, by trying to identify which of all the possible action frameworks may mark the trend on the international stage to be followed with regard to what the commitment of the Armed Forces at large must be and how should they play their role accordingly.


Apesar da heterogeneidade casuística existente no nível internacional com relação ao papel jogado pelas Forças Armadas, a dedicação e uso deles (ou a decisão de não fazê-lo) na luta contra a delinquência organizada no detalhe gera, a hoje, não poucas controvérsias. Os defensores e os detratores usam razões e argumentos para defender o papel que é desejado conceder às Forças Armadas (ou atribuí-las, de acordo com cada caso), como fornecedores da segurança cidadã frente ao crime organizado. Seu uso inicial na confrontação contra o tráfego de drogas em todo o mundo causou o debate sobre a imersão total na luta contra toda tipologia da delinquência organizada, que gerou, de facto, diversos cenários. Pretende-se fazer uma reflexão ao ar dos prós e contras que são derivados da implicação das Forças Armadas na luta contra a criminalidade organizada, extraídos da análise casuéstico dos principais cenários vigentes no mundo, tentando identificar qual dos possíveis marcos de atuação a tendência na cena internacional, sobre o qual deve ser o compromisso das Forças Armadas à frente da criminalidade organizada, e como devem executá-lo.


Assuntos
Atividades Militares/legislação & jurisprudência , Atividades Militares/políticas , Atividades Militares/prevenção & controle , Polícia/normas , Polícia/organização & administração , Polícia
17.
Vision Res ; 86: 27-34, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23597582

RESUMO

The optical properties of the crystalline lens are determined by its shape and refractive index distribution. However, to date, those properties have not been measured together in the same lens, and therefore their relative contributions to optical aberrations are not fully understood. The shape, the optical path difference, and the focal length of ten porcine lenses (age around 6 months) were measured in vitro using Optical Coherence Tomography and laser ray tracing. The 3D Gradient Refractive Index distribution (GRIN) was reconstructed by means of an optimization method based on genetic algorithms. The optimization method searched for the parameters of a 4-variable GRIN model that best fits the distorted posterior surface of the lens in 18 different meridians. Spherical aberration and astigmatism of the lenses were estimated using computational ray tracing, with the reconstructed GRIN lens and an equivalent homogeneous refractive index. For all lenses the posterior radius of curvature was systematically steeper than the anterior one, and the conic constant of both the anterior and posterior positive surfaces was positive. In average, the measured focal length increased with increasing pupil diameter, consistent with a crystalline lens negative spherical aberration. The refractive index of nucleus and surface was reconstructed to an average value of 1.427 and 1.364, respectively, for 633 nm. The results of the GRIN reconstruction showed a wide distribution of the index in all lens samples. The GRIN shifted spherical aberration towards negative values when compared to a homogeneous index. A negative spherical aberration with GRIN was found in 8 of the 10 lenses. The presence of GRIN also produced a decrease in the total amount of lens astigmatism in most lenses, while the axis of astigmatism was only little influenced by the presence of GRIN. To our knowledge, this study is the first systematic experimental study of the relative contribution of geometry and GRIN to the aberrations in a mammal lens.


Assuntos
Cristalino/fisiopatologia , Refração Ocular/fisiologia , Erros de Refração/fisiopatologia , Animais , Astigmatismo/fisiopatologia , Modelos Animais de Doenças , Suínos , Tomografia de Coerência Óptica
18.
Biomed Opt Express ; 3(3): 473-87, 2012 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-22435096

RESUMO

A new technique is presented for the non-invasive imaging of the dynamic response of the cornea to an air puff inducing a deformation. A spectral OCT instrument combined with an air tonometer in a non-collinear configuration was used to image the corneal deformation over full corneal cross-sections, as well as to obtain high speed measurements of the temporal evolution of the corneal apex. The entire deformation process can be dynamically visualized. A quantitative analysis allows direct extraction of several deformation parameters, such as amplitude, diameter and volume of the maximum deformation, as well as duration and speed of the increasing deformation period and the recovery period. The potential of the technique is demonstrated on porcine corneas in vitro under constant IOP for several conditions (untreated, after riboflavin instillation and under cross-linking with ultraviolet light), as well as on human corneas in vivo. The new technique has proved very sensitive to detect differences in the deformation parameters across conditions. We have confirmed non-invasively that Riboflavin and UV-cross-linking induce changes in the corneal biomechanical properties. Those differences appear to be the result of changes in constituent properties of the cornea, and not a consequence of changes in corneal thickness, geometry or IOP. These measurements are a first step for the estimation of the biomechanical properties of corneal tissue, at an individual level and in vivo, to improve diagnosis and prognosis of diseases and treatments involving changes in the biomechanical properties of the cornea.

20.
J Vis ; 10(5): 19, 2010 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-20616133

RESUMO

We measured the effect of the correction of the natural aberrations of the eye by means of adaptive optics on the subject's performance on three different visual tasks: subjective sharpness assessment of natural images, familiar face recognition, and facial expression recognition. Images were presented through a dedicated psychophysical channel and viewed through an electromagnetic deformable mirror. Experiments were performed on 17 normal subjects. Ocular aberrations (astigmatism and higher order aberrations) were reduced on average from 0.366 +/- 0.154 to 0.101 +/- 0.055 mum for a 5-mm pupil diameter. On average, subjects considered to be sharper 84 +/- 14% of the images viewed under AO correction, and there was a significant correlation between the amount of corrected aberrations and the percentage of images that the subject considered sharper when observed under AO-corrected aberrations. In all eyes (except one), AO correction improved familiar face recognition, by a factor of x1.13 +/- 0.12 on average. However, AO correction did not improve systematically facial expression recognition.


Assuntos
Adaptação Fisiológica/fisiologia , Astigmatismo/fisiopatologia , Astigmatismo/reabilitação , Percepção Visual/fisiologia , Adulto , Óculos , Humanos , Curva ROC , Análise e Desempenho de Tarefas , Adulto Jovem
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